muller



' M y 1957 w. c. MULLER ETAL 2,792,432

PROCESS OF HYDROLYZING ETHYLENE-SULFURIC ACID ABSORBATE Filed Oct. 20, 1953 CONDENSER COOLER INVENTOR WERNER C MULLER FRAN/(LHV D. MILLER United States Pa e i PRQCESS OF HYDRGLYZING ETHYLENE- SULFURIC AlD ABSORBATE Werner C. Muller, Roslyn, N. Y., and Franklyn D. Miller, Cincinnati, Ghio, assignors to National Petra-Chemicals Corporation, a corporation of Delaware Application ()ctober 20, 1953, Serial No. 387,202 6 Claims. Cl. 260-639) by cracking a petroleum distillate or natural gas followed by rectification of the cracked product to produce a cut, the olefin content of which is predominantly ethylene. This cut is then absorbed countercurrently in strong sulfuric acid under a pressure of at least 200 lbs. p. s. 'i. g. to produce an absorbate containing both mono and diethyl sulfates and preferably the ethylene content of which ranges from 1.3 to 1.5 mols of ethylene per mol of sulfuric acid. 7

The process of this invention is applicable to any such absorbate in which the alkyl sulfate content consists predominantly of mono and diethyl sulfates. The preferred raw material for the application of this process is an absorbate containing between 1.3 and 1.5 mols of ethylene per mol of sulfuric acid, such as is produced by the ab- SOTPllOIl of a gas consisting predominantly of ethylene in strong sulfuric acid under'a pressure of at least 200 lbs. p. s. i. g. Theinvention will be fully understood from the following description read in conjunction with the drawing WhiCb'iS'Et diagrammatic showing of apparatus in which the invention may be carried out.

Referring to the drawing 1 designates -.a liquid vapor countercurrent contacting device of the type which may be broadly identified as a rectification tower. "T he invention' is of course not limited to use with a rectification type tower since any liquid-vapor countercurrent contacting device, such as a packed column or sieve-tray column, may be similarly employed. v v

The absorbate of the type hereinabove described is introduced through pipe 2 controlled by valve 3. Water for dilution is introduced through pipe 4 controlled by valve 5. The diluted absorbate is introduced at a midpoint of tower 1 through pipe 5. The diluted absorbate is preferably at a temperature between 160 and 220 F. The mount of dilution water is sufficient to dilute the sulfuric acid content of the absorbateicalculated on'a hydrocarbon-free basis) to from 65 weight percent aqueous sulfuric acid. Within the tower 1 the diluted absorbate moves downwardly over a series of horizontally. disposed trays 7 spanning the tower, each of which carries downfiow pipes 8 maintaining a predetermined layer of liquid on each tray, and devices such as bell caps 9 for dispersing rising vapors into the layer ofliquid retained on each tray. In practical operation such a'tower may, for example, contain such trays, although this is intended merely'by way of illustration. Any alternative method of maintaining liquid-vaporcountercurrent contact at a plurality of stages or levels may be similarly used. Provision is made for heating the base 11 of tower 1, for example by introducing steam under pressure through pipe 12 into the base ofthetower. .Flowthrough pipe 12 is controlled by valve 13. Liquid accumulating in base 11 may be withdrawn through pipe 14 controlled by valve 15, which pipe projects upwardly within the tower to retain a pool of liquid in the base thereof. 7

In operation the amount of steam introduced is sufiflcient to boil the liquid in the base of tower 1, thereby causing the evolution of vapors consisting principally of ethyl alcohol, which vapors move upwardly within the tower approaching equilibrium with the liquid upon each tray or at each level, thereby efiiecting transfer of heat upwardly within the tower and maintaining liquid-vapor equilibriums similar to those obtaining in a rectifying column. The amount of steam introduced into the'base of the tower and thereby communicated to the various trays or levels within the tower, is sufficient to initiate and maintain active hydrolysis of the absorbate introduced through pipe 6. The amount of steam necessary for this purpose will range from /2 to 4 mols per mol of sulfate radical introduced with said absorbate. It will of course be understood that this amount of heat may be similarly introduced either in whole or in part by any other heating means. The retention time in the tower is suflicient to produce substantially complete hydrolysis of the dialkyl sulfate and also the major part of the monoalkyl sulfate present.

Vapor is withdrawn from the upper part of tower 1 through pipe 21 controlled by valve 22 and is passed through condenser 23, by which it is principally condensed'to liquid. A part of this is withdrawn from the system through pipe 24 controlled by valve 25 through cooler 26, by which it is transferred to storage through pipe 27. Part of the overhead so condensed is returned through pipe 31 controlled by valve 32 into the upper part of tower i, to maintain refluxing conditions in the upper part of tower 1. Sufiicieut reflux is returned in this Way through pipe 31 to insure that the amount of ethanol present in the condensate withdrawn from the system shall not be more than 25 percent of that currently produced and preferably not over ten percent.

One objective of the process is to insure that the alcohol produced by hydrolysis shall move in a general downwardly direction within tower 1, to be withdrawn in solution in the bottoms carried off through pipe 14 and the amount of reflux returned through pipe 31 is adjusted to accomplish this purpose. There is simultaneously an upward movement of alcohol in vapor phase within tower 1 from tray to tray or from level to level, which operates to transfer heat from the base upwardly within the tower, and to cause the liquid at each level or upon each-tray to applioach equilibrium with'the vapor in contact there- Wll In general, the temperatures obtaining in the base ii of tower 1 will range from 225300 F. and the pressure obtaining within the tower will range from G-lGG lbs. gauge. At any given temperature and pressure after the system has come to equilibrium, an amount of alcohol equal to that produced by hydrolysis (excepting the amount carried out of the system through pipe 27) is present in the bottoms and the bottoms will therefore contain from 10-25 moi percent ethanol calculated on a sulfatefree basis. Moving progressively upward within the tower each tray or level will be at approximately the same temperature, with a relatively uniform mol concentration of ethanol in the liquid-phase. The mol concentration of alcohol on the trays immediately below the inlet pipe 6 will range from 10 to 40'mol percent ethanol calculated on a sulfate-free basis, depending upon the selected operating conditions. -Up to the time the system comes to equilibrium and until this concentration of ethanol is'built up on the plates below inlet pipe 6, the bottoms withdrawn through pipe 14 willco'nta'in less than the amount of ethanol currently produced by by be brought to equilibrium more quickly by the introduc- I tion of ethanol from an external source through pipe 33 controlled by valve 34. In general the amount of ethanol present in the bottoms after the system has come to equilibrium, will be that produced by hydrolysis within the tower,'with the'exception of that withdrawn from the system through pipe 27, and will therefore be at least 75 percent of that currently produced, and preferably at least 90 percent of that currently produced.

The net effect of this mol concentration of ethanol within the reaction zone, i. e., above the base of tower 1 and below inlet pipe 6, is to hold insolution or resolubilize the dialkyl sulfate which would otherwise be present,'at least in part, as a separate phase and thereby to eliminate or minimize the side reactions which would occur if the dialkyl sulfate were present as a separate phase. On the other hand, the presence of excess alcohol tends to move the equilibrium in the direction of ether production by reaction of ethanol with the mono and/or dialkyl sulfate present. To this end we recycle and reintroduce into the tower adjacent the base, through pipe 35 controlled by valve 36, a part of the overhead consisting predominantly of ether. 7 The amount of ether reintroduced in this way ranges from l-l times the amount withdrawn through pipe 27, and is preferably within the range of from 5-10 times the amount withdrawn through pipe 27. We thereby maintain an excess concentration of ether within the reaction zone defined by tower 1 which inhibits the reaction between the ethanol and the mono and/or dialkyl sulfate. In this way. we are able to obtain'the solubilizing effect of the alcohol present while at the same time holding to a minimum the amount of ether concurrently produced. Although the general movement of dialkyl sulfate is downwardly in liquid phase from the pointof introduction of the abs'orbate, owing to its partial pressure it is in generally upward movement in vapor phase from the lower trays or levels. This holdsthe dialkyl sulfate in the reaction zone until hydrolysis is complete and results in substantially complete elimination of the dialkyl sulfate a few trays above the base of the tower.

, The. hydrolysate withdrawn through pipe 14 is passed into the upper section of the liquid vapor countercurrent contacting device 41. This also consists of a tower similar in construction to a so-called rectification tower spanned by a number of horizontal trays carrying downflow pipes 42 and devices,.such as hell caps 43 for dispersing ascending vapor into the pool of liquid retained on each such tray. Provision is made for heating liquid in the base of tower 41 by introducing a heating fluid, such, as steam under pressure, through coil 44 controlled by valves 45 and 46. Alternatively the liquid in the base of tower 41 may be heated by the introduction of live steam. Liquid accumulating in the base of tower 41 is withdrawn through pipe 47 controlled by valve 48,. which pipe projects upwardly within the base 49 of tower 41 to retain a pool of liquid in the base. Tower 41 is operated in the conventional way to complete hydrolysis of the monoethyl sulfate present and to strip the ethanol from the residual acid. This acid, of from 35-65 weight percent (hydrocarbon-free basis) is diverted by pump 51 through pipe 52. The ethanol in vapor phase is withdrawn from the top of tower 41, is conducted away through pipe 53 controlled by valve 54 to condenser 55, following which it is passed in liquid phase through pipe 56 and cooler.57 and thence to storage through pipe 58.

Some ethanol vapor withdrawn from tower 41 through 7 pipe 53 may also be passed through pipe 61 controlled by valve 62 into base 11 of tower 1. This results in transferof heat as latent heat of vaporizationinto tower 1, and to the extent to which this heat is introduced, the steam introduced through pipe 12 may be reduced or eliminated.

"The residual acid passing off through pipe 52 may be diverted from the system for reeoncentration and reuse through pipe 63 controlled by valve 64. It may also, in

'part, be introduced into tower 1 through pipe 65. While the water content of this residual acid cannot be substituted for the water required for hydrolysis, it supplements this water by maintaining conditions in the upper part of tower 1 which increasethe amount of ethanol carried downwardly in the liquid phase and, in general, createsconditions more favorable to complete hydrolysis within the tower.

The following is a specific example of the operation of our process:

This run was carried out in an experimental apparatus corresponding in design to that shown in the figure. The amount of absorbate fed in through pipe 2 was 0.29 mol per hour. The amount .of water fed in through pipe 4 was 1.10 mols per hour. The amount of steam introduced into the base was 0.36 mol per hour. The amount of ether recycled to the base of the tower through pipe 35 was 0.136 mol per hour. 'The amount of ether refluxed through pipe 31 to the top of the tower was 0.09 mol per hour. v

The dimension of the tower was such that the average retentiontime in the tower was 30 minutes and the tower was operated under pressure of 20 lbs. p. s. i. g.

The operating temperatures were as follows: F.

In base .of tower 247 The composition of the overhead leaving the tower through pipe 21 was:

r Weight percent Ether 83 .5 Ethanol 4.9 Water r 5.7 Sulfur dioxide 5.9

The composition of the material withdrawn from the base of the towerthrough pipe 14 was:

i i Weight percent Sulfuric acid A 34.0 Ethanol 17.2 Ether 0.68 Ethyl sulfuric ac 10.5 Water 37.6

A sample of material from approximately the point at which pipe 33 enters the tower 1 analyzed:

' i l i 7 Weight percent H2SO4 31.5 Ethanol 20.65 Ether v 2.33 Ethyl sulfuric d 14.0

Water 31.52

. The composition of'the organic material withdrawn from tower 41throughpipe 53 was:

' Weight percent Ethanol 78.5

Ether 11.3

Polymer 9.4

We claim:'

1. Process 'of hydrolyzing ethylene-sulfuric acid absorbate containing both monoand diethyl sulfates com-- prising introducing 'such absorbate into the, mid-section of aliquid-va'por countercurrent contacting. device, intro ducing water into the mid-section of such device in amount suificient to dilute the sulfuric acid present in such absorbate to a concentration of from 35-65 weight percent (hydrocarbon-free basis), introducingheatinto the base of such device in amount sufiicient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume of said device being coordinated to give an average residence time sufficient to hydrolyze at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the upper end of said device, returning said condensate in part as reflux and conducting said condensate away in part, the amount of condensate returned as reflux being sufiicient to hold the amount of alcohol in the part conducted away at not more than 25% of that currently produced by hydrolysis in said device, the amount of heat introduced into the base of said device being equivalent to that which would be introduced by from /2 to 4 mols of steam for each equivalent of sulfate radical introduced with said absorbate and conducting hydrolysate away from the base of such device.

2. Process of hydrolyzing ethylene-sulfuric acid absorbate containing both monoand diethyl sulfates comprising introducing such absorbate into the mid-section of a liquid-vapor countercurrent contacting device, introducing water into the mid-section of such device in amount sufiicient to dilute the sulfuric acid present in such absorbate to a concentration of from 35-65 weight percent (hydrocarbon-free basis), introducing heat into the base of such device in amount suflicient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume of said device being coordinated to give an average residence time suflicient to hydrolyze at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the upper end of said device, returning said condensate in part as reflux and conducting said condensate away in part, the amount of condensate returned as reflux being suflicient to hold the amount of alcohol in the part conducted away at not more than of that currently produced by hydrolysis in said device, the amount of heat introduced into the base of said device being equivalent to that which would be introduced by from A2 to 4 mols of steam for each equivalent of sulfate radical introduced with said absorbate and conducting hydrolysate away from the base of such device.

3. Process of hydrolyzing ethylene-sulfuric acid absorbate containing both monoand diethyl sulfates comprising introducing such absorbate into the mid-section of a liquid-vapor countercurrent contacting device, introducing water into the mid-section of such device in amount sufficient to dilute the sulfuric acid present in such absorbate to a concentration of from 35-65 weight percent (hydrocarbon-free basis), introducing heat into the base of such device in amount suificient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume of said device being coordinated to give an average residence time suflicient to hydrolyze at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the upper end of said device, returning said condensate in part as reflux, in part by introducing same adjacent the base of said device, and conducting away the remainder, the amount of condensate returned as reflux being sufiicient to hold the amount of alcohol in the part conducted away at not more than 25% of that currently produced by hydrolysis, the amount of such condensate introduced adjacent the base of said device being at least equal in amount to that conducted away, the amount of heat introduced into the base of said device being equivalent to that which would be introduced by from /2 to 4 mols of steam for each '6 equivalent of =su1fate --radic'alintroduced with 'said absorbateand' conducting hydrolysate away from the base of such device.

4. Process of hydrolyzing ethylene-sulfuric acid absorbatecontaining both monoand diethyl sulfates comprising introducing such absorbate into the mid-section of a liquid-vaporcountercurrent contacting device, introducing water into the mid-section of such device in amountsufficient to dilute the sulfuric acid present in such absorbate to a concentration of frorn35-65 weight percent (hydrocarbonree basis), introducing heat into the base of such'device in amount sufficient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume of said device being coordinated to give an average residence time sufficient to hydrolyze at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the upper end of said device, returning said condensate in part as reflux, in part by introducing same adjacent the base of said device, conducting away the remainder, the amount of condensate returned as reflux being suflicient to hold the amount of alcohol in the part conducted away at not more than 25% of that currently produced by hydrolysis, the amount of such condensate introduced adjacent the base of said device ranging from 1 to 15 times the amount conducted away, the amount of heat introduced into the base of said device being equivalent to that which would be introduced by from /2 to 4 mols of steam for each equivalent of sulfate radical introduced with said absorbate and conducting hydrolysis away from the base of such device.

5. Process of hydrolyzing ethylene-sulfuric acid absorbate containing both monoand diethyl sulfates comprising introducing such absorbate into the mid-section of a liquid-vapor countercurrent contacting device, intro ducing water into the mid-section of such device in amount suificient to dilute the sulfuric acid present in such absorbate to a concentration of from 35-65 weight percent (hydrocarbon-free basis), introducing heat into the base of such device in amount sufficient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume of said device being coordinated to give an average residence time sufiicient to hydrolyze at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the upper end of said device, returning said condensate in part as reflux, in part by introducing same adjacent the base of said device, and con-ducting away the remainder, the amount of condensate returned as reflux being sufiicien't to hold the amount of alcohol in the part conducted away at not more than 10% of that currently produced by hydrolysis, the amount of such condensate introduced adjacent the base of said device being at least equal in amount to that conducted away, the amount of heat introduced into the base of said device being equivalent to that which would he introduced by from /2 to 4 mols of steam for each equivalent of sulfate radical introduced with said absorbate and conducting hydrolysate away from the base of such device.

6. Process of hydrolyzing ethylene-sulfuric acid absorbate containing both monoand diethyl sulfates comprising introducing such absorbate into the mid-section of a liquid-vapor countercurrent contacting device, introducing water into the mid-section of such device in amount sufficient to dilute the sulfuric acid present in such absorbate to a concentration of from 3565 weight percent (hydrocarbon-free basis), introducing heat into the base of such device in amount suiiicient to maintain boiling in the base thereof and vapors moving progressively upward in equilibrium with liquid from the base to the top of said device, the amount of feed and the volume .7 ofsaid device being'coordinated -tOrgiV an average residence time sufiicient to hydrolyze-at least the major portion of the diethyl sulfate in said feed, condensing vapors adjacent the- "upper end of said device, returning said condensate in part as reflux, in part by introducing same adjacent the base of said device,- conducting away the remainder, the amount of condensate returned as reflux being suificient to hold the amount of alcohol in the part conducted away at not more than 10% of that currently produced by hydrolysis, the amount of such condensate introduced adjacent the base of said device ranging from 1 to 15 times the amount conducted away, the amount of heat introduced into the base of said device being References Cited in the file of this patent UNITED STATES PATENTS 1,868,076 Ricard July 19, 1932 2,105,508 Rosen et a1. Jan. 18, 1938 2,474,568 Bannon et a1. June 28, 1949 2,541,673 Smith Feb.v 13, 1951 

1. PROCESS OF HYDROLYZING ETHYLENE-SULFURIC ACID ABSORBENT CONTAINING BOTH MONO- AND DIETHYL SULFATES COMPRISING INTRODUCING SUCH ABSORBATE INTO THE MID-SECTION OF A LIQUID-VAPOR COUNTERCURRENT CONTACTING DEVICE, INTRODUCING WATER INTO THE MID-SECTION OF SUCH DEVICE IN AMOUNT SUFFICIENT TO DILUTE THE SULFURIC ACID PRESENT IN SUCH ABSORBATE TO A CONCENTRATION OF FROM 35-65 WEIGHT PERCENT (HYDROCARBON-FREE BASIS), INTRODUCING HEAT INTO THE BASE OF SUCH DEVICE IN AMOUNT SUFFICIENT TO MAINTAIN BOILING IN THE BASE THEREOF AND VAPORS MOVING PROGRESSIVELY UPWARD IN EQUILIBRIUM WITH LIQUID FROM THE BASE, TO THE TOP OF SAID DEVICE, THE AMOUNT OF FEED AND THE VOLUME OF SAID DEVICE BEING COORDINATED TO GIVE AN AVERAGE RESIDENCE TIME SUFFICIENT TO HYDROLYZE AT LEAST THE MAJOR PORTION OF THE DIETHYL SULFATE IN SAID FEED, CONDENSING VAPORS ADJACENT THE UPPER END OF SAID DEVICE, RETURNING SAID CONDENSATE IN PART AS REFLUX AND CONDUCTING SAID CONDENSATE AWAY IN PART, THE AMOUNT OF CONDENSATE 